In northern ponds with a higher probability for winter kill, the deeper the pond the better. With you being in FL where winter kill isn't an issue, I would say as long as you have a good area of water around 6', you are good. Much of the year in FL, your pond will be stratified and the deeper areas of the pond will be of no value anyways. Now if you use an aerator, that can change. Even then I don't think deeper pond in the far south are necessary for most goals. Particularly for a LMB/BG pond.
As far as the aquatic vegetation infestation, walk the edge of the pond and try to determine the slope of it as it goes into the pond. A fairly steep slope would be ideal limiting the amount of shallow water and reducing the growth of shoreline aquatics like cattails as well as submerged aquatic vegetation. A 2:1 slope is ideal.
